Note: Descriptions are shown in the official language in which they were submitted.
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SEAT ASSEMBLY FOR AN OFFICE CHAIR
FIELD OF THE INVENTION
[0001] The invention relates to an improved seat assembly,
and more particularly, to a seat assembly having an improved
connector structure for securing a cushion-enclosing cover to
a seat shell.
BACKGROUND OF THE INVENTION
[0002] Conventional office chairs use a variety of
constructions for the seat assembly. Many such chairs use a
sheet-like molded shell which mounts to a chair base wherein
the shell supports a cushion and then a seat cover which
overlies the cushion to provide the aesthetic finished
appearance of the seat assembly. The cover may be formed from
a variety of materials and often is formed of a fabric that
can be selectively varied depending upon the pattern desired
by a purchaser. In such chairs, it is necessary to secure the
peripheral edge of the cover, often to the seat shell or other
seat structure. In some chair constructions, separate
fasteners such as staples and the like may be used to secure
the peripheral edge to the inner shell.
[0003] It is an object of the invention to provide an
improved seat assembly for a cushioned seat having an improved
construction for securing the peripheral edge of the seat
cover.
[0004] The invention relates to improved attachment
structure for securing a cover in overlying covering relation
to a seat cushion. In the chair of the invention, the chair
comprises a seat/back assembly having a seat assembly and back
assembly which are supported upon a load-bearing base adapted
for support upon a floor. This base may include a tilt
control mechanism wherein the seat assembly and back assembly
are pivotally connected to the tilt control mechanism and
rearwardly reclinable in operation. The seat assembly itself
has front and rear seat portions that pivotally connect to the
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tilt control mechanism supported on the base. To support the
seat loads, the seat assembly comprises a structurally rigid
support plate which is horizontally enlarged and formed of a
structurally rigid material such as metal, wherein the front
and rear edge portions of the seat plate pivotally connect to
the seat or to the tilt control mechanism so that the seat
assembly is rearwardly tiltable in operation.
[0005] The seat assembly further comprises a horizontally
enlarged, inner shell which has a bottom surface which is
supported by the seat plate, and an upper surface which
preferably is covered with a resiliently-compressible cushion.
This cushion extends outwardly to the outer peripheral edge of
the inner shell and in turn is enclosed by a seat cover, for
example, formed of a fabric material, which seat cover is
enlarged widthwise and in the front-to-back direction so as to
hang over the sides of the cushion and wrap about the outer
peripheral edge of the inner shell. As such, the peripheral
cover edge is able to wrap about and extend partially
underneath the bottom of the inner shell. In this edge
region, the inner shell includes an edgewise-extending
securement channel defined by parallel, downwardly-projecting
channel walls. The inner channel wall includes spaced-apart
teeth which preferably are tapered so as to facilitate
compression of the cover material.
[0006] An annular outer shell is provided which mounts to
the inner shell from the underside thereof and extends about
the outer periphery of the inner shell. This outer shell
includes an upstanding rib that extends edgewise about the
periphery of the outer shell and preferably is formed of
aligned ribs which are separated from each other by cross-
windows. In this manner, the individual ribs are edgewise
elongate so as to be generally parallel to the inner and outer
channel walls of the outer shell while the individual ribs may
also have some cross-wise flexure. The free ends of the ribs
include additional teeth so that when the outer shell is
pressed or fitted onto the inner shell from below, the
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peripheral cover edge follows a convoluted or treacherous path
by wrapping about the outer edge of the inner shell and
overlapping the underside of the inner shell, and then
turning upwardly into the channel or valley as it wraps over
the free ends of the ribs, and then turns downwardly out of
the channel and finally extends over and terminates beyond the
inner channel wall and the teeth thereof.
[0007] As the fabric passes cross-wise through this
convoluted path, the cover is pinched at pinch points, wherein
one pinch point preferably is located between the teeth at the
upper ends of the ribs and the opposing bottom surface of the
valley, and a further pinch point is located at the teeth on
the inner channel wall which presses the fabric against an
opposing inside surface of the outer shell. Hence, the cover
material is pinched at multiple locations along the cross-wise
extend of the convoluted path and thereby fixedly secured at
the edge of the cover in compressed, pinched engagement
between opposing surfaces of the outer shell and inner shell.
[0008] Additionally, the individual ribs are separated
edge-wise by the cross-windows wherein the interior of the
securement channel also includes upstanding cross-ribs which
extend between the inner and outer channel walls in crosswise
relation and fit into the cross-windows which thereby forces
the soft cover material into the cross-windows and defines
additional folds along the convoluted path of the cover
material. This provides additional fixed securement of the
cover when compressed between the outer shell and inner shell.
[0009] To potentially define an additional pinch point, the
separation of the individual ribs from each other by the
cross-windows preferably allows for outward flexing of the
individual ribs when the cover material is pulled taut on the
seat. Sufficient cross-wise deflection of the ribs will occur
until the outer side surface of each rib contacts the interior
face of the outer channel wall which thereby would serve to
define an additional pinch point by pinching the cover
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material sidewardly or cross-wise between the rib and the
outer channel wall.
[0010] The securement structure provides an improved method
of securing a cover about its peripheral edge to an outer and
inner shell on a seat assembly. While this structure is
primarily provided for a seat assembly, a back assembly might
also be configured using such securing structure.
[0011] Other objects and purposes of the invention, and
variations thereof, will be apparent upon reading the
following specification and inspecting the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 is a perspective view of a chair of the
invention.
[0013] Figure 2 is a side elevational view thereof.
[0014] Figure 3 is an exploded view of the seat assembly.
[0015] Figure 4 is a front cross-sectional view of the
joined shells.
[0016] Figure 5 is a side cross-sectional view thereof.
[0017]
[0018] Figure 6 is a plan view of a shell assembly.
[0019] Figure 7 is a bottom view of an inner shell of the
shell assembly.
[0020] Figure 8 is an enlarged partial view of the inner
shell.
[0021] Figure 9 is a top perspective view of an outer
shell.
[0022] Figure 10 is an enlarged partial view of the inner
and outer shells.
[0023] Figure 11 is a side cross-sectional view of the
joined shells.
[0024] Figure 12 is a side cross-sectional view thereof.
[0025] Figure 13 is an enlarged perspective view of the
joined inner and outer shells taken from the front.
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[0026] Figure 14 is a partial side cross-sectional view
taken at a rear of the chair.
[0027] Figure 15 is a side cross-sectional view taken at
the front of the chair.
[0028] Certain terminology will be used in the following
description for convenience and reference only, and will not
be limiting. For example, the words "upwardly", "downwardly",
"rightwardly" and "leftwardly" will refer to directions in the
drawings to which reference is made. The words "inwardly" and
"outwardly" will refer to directions toward and away from,
respectively, the geometric center of the arrangement and
designated parts thereof. Said terminology will include the
words specifically mentioned, derivatives thereof, and words
of similar import.
DETAILED DESCRIPTION
[0029] Referring to Figures 1 and 2, the invention relates
to a chair 10 having a pedestal base 11 which comprises a tilt
control mechanism 12 having a seat/back assembly 14 pivotally
connected thereto. The seat/back assembly 14 comprises a pair
of uprights or support arms 15 which are pivotally connected
at their front ends to the tilt control mechanism 12, and have
rearward ends which support a back assembly 16 projecting
vertically upwardly therefrom. Additionally, the seat/back
assembly 14 includes a seat assembly 17 that is pivotally
connected to the uprights 15 and the tilt control mechanism 12
so that the back assembly 16 and seat assembly 17 are
rearwardly tiltable. The invention relates to improvements in
the seat assembly 17.
[0030] Referring to Figures 2 and 3, the seat assembly 17
is pivotally connected by its four corners to front pivot
connections 18 to the tilt control mechanism 12, and rear
pivot connections 19 at the upper ends of upwardly extending
support arms 20 (Figure 2) respectively provided on the
uprights 15. In particular, the seat assembly 17 comprises a
horizontally enlarged rigid support plate 22 which is formed
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of a rigid metal construction and has rear pivot mounts 23
which interconnect to the rear pivot connectors 19 (Figure 2).
The seat plate 22 also includes guide slots 24 which
interconnect with the slidable pivot connectors 18 so that the
front edge of the seat assembly 17 may displace rearwardly to
a small extent therewith during rearward tilting of the
uprights 15. The support plate 22 has a generally
rectangular, pan-like shape which provides a rigid support
surface 22A on the top thereof for carrying the loads of an
occupant sitting on the seat assembly 17.
[0031] In the chair 10 of the invention, the back assembly
16 preferably includes a thin, suspension membrane 24 that
supports the back of a chair occupant. The seat assembly 17
has a different construction in that the seat assembly 17
includes a seat cushion 25 that is relatively thick and is
compressible to conform to the contours of the chair occupant.
[0032] Referring to Figure 3, this cushion 25 generally
comprises an interior cushion layer 26 and a sheet-like
flexible cover 27 that preferably is formed of a fabric
material that defines a suitable exposed surface of the seat
assembly 17. The cover 27 is generally illustrated in Figure
3 and is shaped so as to overlie the cushion. This cover 27
comprises a central portion 28 and a peripheral cover edge 29
that is configured to extend over the peripheral cushion edge
30 of the cushion layer 26. The peripheral cover edge 29 is
configured to be fixedly secured to the seat assembly 17 in an
improved manner which represents an inventive advantage over
prior securement methods for fabric covers of this type.
[0033] More particularly, the seat assembly 17 comprises a
horizontally enlarged inner shell 32 having a top surface 33
that is substantially covered by the cushion layer 26. The
inner shell 32 further defines a downward-facing bottom
surface 34 which is configured to fit onto the support plate
22 and is supported by such support plate 22 in the central
region thereof. The inner shell 32 further defines an outer
peripheral shell edge 35 which generally conforms to the
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peripheral cushion edge 30 in its shape. The size of the
cover 27 is oversized relative to the edges 30 and 35 so that
the peripheral edge portion 29 of the cover 27 is able to wrap
about and extend beneath the bottom shell surface 34 for
subsequent connection thereto.
[0034] In this regard, the seat assembly 17 further
comprises a ring-like outer shell 40 which is defined by an
outer shell edge 41, an inner shell edge 42 as well as top and
bottom surfaces 43 and 44. The outer shell edge 41 is shaped
and sized so that it conforms closely to the shape and size of
the cushion edge 30 and inner shell edge 34. The interior
shell edge 42 of the outer shell 40, however, is dimensioned
larger than the support plate 22 so that this interior shell
edge 42 is spaced outwardly of the support plate 22 and the
support plate 22 in turn is able to pivotally connect to the
tilt control mechanism 12 and uprights 15 as described above.
[0035] Referring to Figures 4 and 5, the inner shell 32
includes the cushion layer 30 thereon as diagrammatically
illustrated, and also includes the cover 27 which overlies the
cushion material 30 and. has its peripheral edge 29 wrapped
downwardly around the outer shell edge 35 so as to thereby
extend underneath the bottom shell surface 34 and be
sandwiched between the inner shell 32 and the underlying outer
shell 40 which is fitted below the bottom shell surface 34.
In particular, the outer shell edge 41 is disposed so as to be
closely adjacent and contact the outer shell edge 35 so that
the peripheral cover edge 29 can extend into the space and be
completely hidden from the exterior of the chair 10 which
provides a clean appearance to the overall seat construction.
[0036] In this regard, it is necessary to ensure that the
peripheral cover edge 29 is not able to pull free from the
inner shell 32. In this regard, the peripheral cover edge 29
extends into the space between the inner shell 32 and outer
shell 40 and extends along a torturous or convoluted path
which securely engages the cover edge 29 so as to be
compressed at one or more locations along such convoluted path
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to resist slippage of the cover edge 29 from the interface
between the inner shell 32 and outer shell 40. Further, as
will be described in further detail hereinafter, the tortuous
or convoluted path as defined by the inventive connector
structure forms convolutions in both a crosswise direction of
the cover edge 29 which can extend either widthwise across the
lateral width or front to back width of the fabric, or
edgewise along the edgewise-extending cover edge 29. By
forming convolutions in the crosswise and edgewise directions,
the connection provides a strong interconnection with the
cover edge 29 to prevent pulling separation of the cover 27
from the interface between the inner shell 32 and outer shell
40.
[0037] As to the outer shell shown in Figures 6-8, this
outer shell 32 is adapted to receive the outer shell 40 in
facing relation on the underside 34 thereof. In this regard,
the bottom shell side 34 includes upstanding connector posts
45 at spaced-apart locations about the outer shell edge 35 for
fastening to the outer shell 40. The inner shell 32 further
comprises an edgewise-extending connector channel or valley 46
which is defined by front and back channel sections 46A and
46B as well as opposite side sections 46C and 46D. These
channel sections 46A-46D generally have similar constructions
although the overall shape may vary depending upon the
requirements and components provided in the seat assembly 17.
As seen in the enlarged view of Figures 8 and 13, the
connector channel 46 is defined by inner and outer channel
walls 47 and 48 and a bottom wall 49. The channel 46 is
continuous along the length of the entire channel 46 at least
proximate the downward-opening mouth of the channel 46. The
bottom of the channel 46, however, which is defined adjacent
the bottom wall 49, is segmented by cross-ribs 50 as seen
generally in Figure 8, and illustrated in greater detail in
Figures 11-13. This forms a plurality of separated pockets 51
which are separated from each other by the cross-ribs 50. The
pockets 51 hereby are defined edgewise by the spaced-apart
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cross-ribs 50, as well as crosswise by the inside faces of the
inner and outer channel walls 47 and 48. These pockets 51 and
cross-ribs 50 help define the convoluted path and the
convolutions thereof in the crosswise direction and the
edgewise direction. Since the channel 46 extends about the
entire periphery of the inner shell 35, the crosswise
direction extends between the inside faces of the inner and
outer channel walls 47 and 48. As such, the crosswise
direction in channel sections 46D and 46C would extend
widthwise, while the crosswise direction in the channel
sections 46A and 46B would extend in the front-to-back
directions.
[0038] To further affix the cover edge 29, the middle edge
52 of the inner channel wall 47 is formed with a plurality of
edgewise spaced projections or teeth 53 that preferably are
formed as pointed or cone-shaped projections. As seen in
Figures 13-15, the cover edge 29 extends over the wall edge 52
and is pinched by the projections 53 which project downwardly
and are disposed closely adjacent if not disposed in contact
with the inner face of the outer shell 40.
[0039] More particularly as to the outer shell 40, such
shell 40 is formed with a peripheral rib structure 60 defined
by front and rear rib sections 60A and 60B and side rib
sections 60C and 60D. These rib sections 60A-60D of the rib
structure 60 are each defined by separated, rectangular ribs
61 which project upwardly and are separated from each other by
windows 62. Figures 11 and 12 clearly illustrate the
individual ribs 61 and window 62 wherein the ribs 61 fit into
the individual pockets 51 while the windows 62 accommodate the
cross-ribs 50 described above. The individual ribs 60 also
include upright conical or pointed teeth or projections 63,
which project upwardly and are disposed closely adjacent the
bottom channel surface defined by the bottom channel wall 49.
These teeth 63 thereby pinch the cover 27 tightly against the
channel bottom wall 49 while the inward section of the cover
27 also is pinched by the respective teeth 53 formed on the
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inner channel 47 as seen in Figure 13. These structures
thereby firmly secure the cover edge 29 in place.
[0040] In particular, the cover 27 follows a convoluted
path in both the edgewise direction as seen in phantom outline
in Figure 12 and also follows a convoluted path in the
crosswise direction as seen in phantom outline in Figure 13.
These paths extend sidewardly but then turn vertically
downwardly or upwardly and then reverse directions and turn in
the opposite downward or upward direction until then again
turning sidewardly or horizontally. In the edgewise
direction, the convoluted path is generally U-shaped (Figure
12) as the cover 27 extends through each window 62 and around
the bottom edge of the cross-ribs 50. In Figure 13, the
convoluted path defines an inverted U shape as the fabric 27
extends upwardly over the top edge and teeth 63 provided on
the ends of the ribs 61. The crosswise convoluted path is
also seen in Figure 14 at the rear edge of the seat assembly
17, and in Figure 15 at the front edge of the seat assembly
17. The edgewise convoluted path of Figure 12 is also created
at the seat back edge (Figure 14) and at the seat front edge
(Figure 15).
[0041] Additionally, the close engagement of the respective
teeth 53 and 63 against opposing shell surfaces creates pinch
points at at least two locations along the crosswise width of
the edge portion 29. When the seat assembly 17 is occupied,
it is expected that this may thereby tension and pull the
cover 27 outwardly in the direction of reference arrow 65
(Figure 13) which would tend to attempt to withdraw the fabric
edge 29 from the above-described connector structure.
However, the above-described tortuous or convoluted path of
the fabric edge 29 in the crosswise and edgewise directions
will prevent undesirable stretching of the cover 27 away from
this connector structure. If some stretching or displacement
of the fabric 27 does occur, it is anticipated that the ribs
61 may also deflect inwardly as diagrammatically seen in
Figure 13 until the upper edge of the rib 61 contacts the
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inside face of the inner channel wall 48. This is then
expected to create a further pinch point at location 66 and
the pinching force would increase in direct relation to the
pulling force by which the cover 27 is subjected by occupant
loads. In this manner, the above-described connector
structure provides secure engagement of the cover 27 within
the interface between the inner shell 32 and the outer shell
40.
[0042] During assembly, the outer cover 40 also includes
fastener holes 75 that align with the afore-mentioned posts 45
on the inner shell 32 so that the inner shell 32 and outer
shell 40 are screwed together and tightly secure the fabric
edge 29 as described above. This then forms a sub-assembly of
the shells 32 and 40, the cushion layer 30 and the cover 27
which in turn can be mounted to the support plate 22 by
appropriate fasteners.
[0043] Although a particular preferred embodiment of the
invention has been disclosed in detail for illustrative
purposes, it will be recognized that variations or
modifications of the disclosed apparatus, including the
rearrangement of parts, lie within the scope of the present
invention.
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